IEEE 1394 interface - AbsoluteAstronomy.com

The IEEE 1394 interface is a serial bus

Serial communications

In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels...

interface standard

Interface standard

In telecommunications, an interface standard is a standard that describes one or more functional characteristics or physical characteristics necessary to allow the exchange of information between two or more systems or pieces of equipment.An...

for high-speed communications and isochronous

Isochronous

Isochronous : From Greek iso, equal + chronos, time. It literally means regularly, or at equal time intervals. In general English language, it refers to something that occurs at a regular interval, of the same duration; as opposed to synchronous which refers to more than one thing happening at the...

real-time data transfer, frequently used by personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s, as well as in digital audio

Digital audio

Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...

, digital video

Digital video

Digital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...

, automotive, and aeronautics

Aeronautics

Aeronautics is the science involved with the study, design, and manufacturing of airflight-capable machines, or the techniques of operating aircraft and rocketry within the atmosphere...

applications. The interface is also known by the brand names of FireWire (Apple), i.LINK (Sony

Sony

, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

), and Lynx (Texas Instruments

Texas Instruments

Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

). IEEE 1394 replaced parallel SCSI

Parallel SCSI

Parallel SCSI is one of the interface implementations in the SCSI family. In addition to being a data bus, SPI is a parallel electrical bus: There is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it...

in many applications, because of lower implementation

Implementation

Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy.-Computer Science:...

costs and a simplified, more adaptable cabling system. The 1394 standard also defines a backplane

Backplane

A backplane is a group of connectors connected in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete...

interface, though this is not as widely used.

IEEE 1394 is the High-Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control. FireWire is also available in wireless, fiber optic

Optical fiber

An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...

, and coaxial

Coaxial cable

Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...

versions using the isochronous protocols.

Nearly all digital camcorders have included a four conductor 1394 cable interface, though, except for premium models, such inclusion is becoming less common. It remains the primary transfer mechanism for high-end professional audio and video equipment. Since 2003, many computers intended for home or professional audio/video use have built-in FireWire/i.LINK ports, especially prevalent with Sony and Apple's computers. The legacy (alpha) 1394 port is also available on premium retail motherboards.

History and development

FireWire is Apple's name for the IEEE 1394 High Speed Serial Bus. It was initiated by Apple (in 1986) and developed by the IEEE P1394 Working Group, largely driven by contributions from Apple, although major contributions were also made by engineers from Texas Instruments

Texas Instruments

Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

, Sony, Digital Equipment Corporation

Digital Equipment Corporation

Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

, IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

, and INMOS

INMOS

Inmos Limited was a British semiconductor company, founded by Iann Barron, with both the head office and the design office at Aztec West in Bristol, it was incorporated in November 1978.- Products :...

/SGS

SGS

SGS is a three letter acronym that can stand for:* Serene Global Services Pvt.Ltd* Seattle Girls' School* SGS Industrial Services* SGS S.A.* Società Generale Semiconduttori - Aquila Tubi E Semiconduttori , later SGS Microelettronica, a former Italian company now merged into STMicroelectronics* Small...

Thomson

Thomson SA

Technicolor SA , formerly Thomson SA and Thomson Multimedia, is a French international provider of solutions for the creation, management, post-production, delivery and access of video, for the Communication, Media and Entertainment industries. Technicolor’s headquarters are located in Issy les...

(now STMicroelectronics

STMicroelectronics

STMicroelectronics is an Italian-French electronics and semiconductor manufacturer headquartered in Geneva, Switzerland.While STMicroelectronics corporate headquarters and the headquarters for EMEA region are based in Geneva, the holding company, STMicroelectronics N.V. is registered in Amsterdam,...

).

IEEE 1394 is a serial bus architecture for high-speed data transfer. Compared to older avionics

Avionics

Avionics are electronic systems used on aircraft, artificial satellites and spacecraft.Avionic systems include communications, navigation, the display and management of multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles...

data buses such as MIL-STD-1553

MIL-STD-1553

MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the mechanical, electrical, and functional characteristics of a serial data bus. It was originally designed for use with military avionics, but has also become commonly used in spacecraft on-board...

, FireWire is a serial

Serial communication

bus, meaning that information is transferred one bit at a time. Parallel buses utilize a number of different physical connections, and as such are usually much less efficient, more costly, and typically heavier. FireWire fully supports both isochronous

Isochronous

and asynchronous applications.

Apple intended FireWire to be a serial replacement for the parallel SCSI bus while providing connectivity for digital audio and video equipment. Apple's development began in the late 1980s, later presented to the IEEE, and was completed in 1995. As of 2007, IEEE 1394 is a composite of four documents: the original IEEE Std. 1394-1995, the IEEE Std. 1394a-2000 amendment, the IEEE Std. 1394b-2002 amendment, and the IEEE Std. 1394c-2006 amendment. On June 12, 2008, all these amendments as well as errata and some technical updates were incorporated into a superseding standard IEEE Std. 1394-2008.

Apple's internal long-time code-name for FireWire was "Chefcat" starting in 1988 as the team sat around a conference table contemplating what to call the project and staring at Kliban's famous artwork on Michael Johas Teener's coffee mug. That was the "aha" moment articulating the goals of the new interconnect, at low cost and ultimate simplicity presented to the user to replace and unify all other PC interconnections and expand beyond that base to enable ultimate miniaturization of electronics. The concept of the current loop electronics that became the now pervasive LVDS was code named "Greyhound" around 1992.

Sony's implementation of the system, "i.LINK", used a smaller connector with only the four signal conductors, omitting the two conductors which provide power to the device in favor of a separate power connector. This style was later added into the 1394a amendment. This port is sometimes labeled "S100" or "S400" to indicate speed in Mbit/s.

The system is commonly used for connection of data storage device

Data storage device

thumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....

s and DV

DV is a format for the digital recording and playing back of digital video. The DV codec was launched in 1995 with joint efforts of leading producers of video camcorders....

(digital video) cameras, but is also popular in industrial systems for machine vision

Machine vision

Machine vision is the process of applying a range of technologies and methods to provide imaging-based automatic inspection, process control and robot guidance in industrial applications. While the scope of MV is broad and a comprehensive definition is difficult to distil, a "generally accepted...

and professional audio systems. It is preferred over the more common USB for its greater effective speed and power distribution capabilities. Perhaps more important, FireWire uses all SCSI capabilities and has high sustained data transfer rates, important for audio and video editors. Benchmarks show that the sustained data transfer rates are higher for FireWire than for USB 2.0, but lower than USB 3.0

USB 3.0

USB 3.0 is the second major revision of the Universal Serial Bus standard for computer connectivity.USB 3.0 has transmission speeds of up to 5 Gbit/s, which is 10 times faster than USB 2.0 . USB 3.0 significantly reduces the time required for data transmission, reduces power consumption, and...

. Results are marked on Apple Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

but more varied on Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

.

However, the expensive hardware needed to implement it (US$1–$2) has prevented FireWire from displacing USB in low-end mass-market computer peripherals, where product cost is a major constraint.

Under the license offered by MPEG LA

MPEG LA

MPEG LA, LLC, is a Denver-based firm that licenses patent pools covering essential patents requiredfor use of the MPEG-2, MPEG-4 Visual , IEEE 1394, VC-1, ATSC and AVC/H.264 standards...

, a royalty of US$0.25 per unit is payable upon the manufacture of each 1394 product.

Technical specifications

FireWire can connect up to 63 peripherals in a tree or daisy-chain topology

Network topology

Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....

(as opposed to Parallel SCSI's electrical bus topology). It allows peer-to-peer

Peer-to-peer

Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...

device communication — such as communication between a scanner and a printer — to take place without using system memory or the CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

. FireWire also supports multiple hosts

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

per bus. It is designed to support plug and play but not hot swapping

Hot swapping

Hot swapping and hot plugging are terms used to describe the functions of replacing computer system components without shutting down the system...

. The copper cable it uses in its most common implementation can be up to 4.5 metres (14.8 ft) long and is more flexible than most parallel SCSI

Parallel SCSI

cables. In its six-conductor or nine-conductor variations, it can supply up to 45 watts of power per port at up to 30 volts, allowing moderate-consumption devices to operate without a separate power supply.

FireWire devices implement the ISO/IEC 13213 "configuration ROM" model for device configuration and identification, to provide plug-and-play

Plug-and-play

In computing, plug and play is a term used to describe the characteristic of a computer bus, or device specification, which facilitates the discovery of a hardware component in a system, without the need for physical device configuration, or user intervention in resolving resource conflicts.Plug...

capability. All FireWire devices are identified by an IEEE EUI-64 unique identifier in addition to well-known codes indicating the type of device and the protocols it supports.

FireWire devices are organized at the bus in a tree topology. Each device has a unique self-id. One of the nodes is elected root node and always has the highest id. The self-ids are assigned during the self-id process, which happens after each bus resets. The order in which the self-ids are assigned is equivalent to traversing the tree depth-first

Depth-first search

Depth-first search is an algorithm for traversing or searching a tree, tree structure, or graph. One starts at the root and explores as far as possible along each branch before backtracking....

, post-order.

FireWire is capable of safely operating critical systems due to the way multiple devices interact with the bus and how the bus allocates bandwidth to the devices. FireWire is capable of both asynchronous and isochronous

Isochronous

transfer methods at once. Isochronous

Isochronous

data transfers are transfers for devices that require continuous, guaranteed bandwidth. In an aircraft, for instance, Isochronous

Isochronous

devices include control of the rudder, mouse operations and data from pressure sensors outside the aircraft. All these elements require constant, uninterrupted bandwidth. To support both elements, FireWire dedicates a certain percentage to isochronous

Isochronous

data and the rest to asynchronous data. In IEEE 1394 80% of the bus is reserved for isochronous

Isochronous

cycles, leaving asynchronous data with a minimum of 20% of the bus.

Encoding scheme

FireWire uses Data strobe encoding

Data strobe encoding

Data strobe encoding is an encoding scheme for transmitting data in digital circuits.It uses two signal lines , Data and Strobe...

(D/S encoding). In D/S encoding, two non-return-to-zero

Non-return-to-zero

In telecommunication, a non-return-to-zero line code is a binary code in which 1's are represented by one significant condition and 0's are represented by some other significant condition , with no other neutral or rest condition. The pulses have more energy than a RZ code...

(NRZ) signals are used to transmit the data with high reliability. The NRZ signal sent is fed with the clock signal through an XOR gate

XOR gate

The XOR gate is a digital logic gate that implements an exclusive or; that is, a true output results if one, and only one, of the inputs to the gate is true . If both inputs are false or both are true , a false output results. Its behavior is summarized in the truth table shown on the right...

, creating a strobe signal. This strobe is then put through another XOR gate along with the data signal to reconstruct the clock. This in turn acts as the bus's PLL for synchronization purposes.

Arbitration

The process of the bus deciding which node gets to transmit data at what time is known as arbitration

Arbitration

Arbitration, a form of alternative dispute resolution , is a legal technique for the resolution of disputes outside the courts, where the parties to a dispute refer it to one or more persons , by whose decision they agree to be bound...

. Each arbitration round lasts about 125 micro-seconds. During the round, the root node (device nearest the processor) sends a cycle start packet. All nodes requiring data transfer respond, with the closest node winning. After the node is finished, the remaining nodes take turns in order. This repeats until all the devices have used their portion of the 125 micro-seconds, with isochronous

Isochronous

transfers having priority. Up to 80% of the time can be given to isochronous

Isochronous

nodes.

Standards and versions

The previous standards and its three published amendments are now incorporated into a superseding standard, IEEE 1394-2008. The features individually added give a good history on the development path.

FireWire 400 (IEEE 1394-1995)

The original release of IEEE 1394-1995 specified what is now known as FireWire 400. It can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates (the actual transfer rates are 98.304, 196.608, and 393.216 Mbit/s, i.e., 12.288, 24.576 and 49.152 megabyte

Megabyte

The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

s per second respectively). These different transfer modes are commonly referred to as S100, S200, and S400.

Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chain

Daisy chain (electrical engineering)

In electrical and electronic engineering a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring...

ed using active repeaters; external hubs, or internal hubs are often present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 metres (236.2 ft). The 6-conductor connector is commonly found on desktop computers, and can supply the connected device with power.

The 6-conductor powered connector, now referred to as an alpha connector, adds power output to support external devices. Typically a device can pull about 7 to 8 watts from the port; however, the voltage varies significantly from different devices. Voltage is specified as unregulated and should nominally be about 25 volts (range 24 to 30). Apple's implementation on laptops is typically related to battery power and can be as low as 9 V.

Improvements (IEEE 1394a-2000)

An amendment, IEEE 1394a, was released in 2000, which clarified and improved the original specification. It added support for asynchronous streaming

Streaming media

Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...

, quicker bus reconfiguration, packet concatenation

Packet concatenation

Packet concatenation is a computer networking optimization that coalesces multiple packets under a single header....

, and a power-saving suspend mode.

IEEE 1394a offers a couple of advantages over IEEE 1394. 1394a is capable of arbitration accelerations, allowing the bus to accelerate arbitration cycles to improve efficiency. It also allows for arbitrated short bus reset, in which a node can be added or dropped without causing a big drop in isochronous transmission.

1394a also standardized the 4-conductor alpha connector developed by Sony and trademarked as "i.LINK", already widely in use on consumer devices such as camcorders, most PC laptops, a number of PC desktops, and other small FireWire devices. The 4-conductor connector is fully data-compatible with 6-conductor alpha interfaces but lacks power connectors.

FireWire 800 (IEEE 1394b-2002)

IEEE 1394b-2002 introduced FireWire 800 (Apple's name for the 9-conductor "S800 bilingual" version of the IEEE 1394b standard). This specification and corresponding products allow a transfer rate of 786.432 Mbit/s full-duplex via a new encoding scheme termed beta mode. It is backwards compatible to the slower rates and 6-conductor alpha connectors of FireWire 400. However, while the IEEE 1394a and IEEE 1394b standards are compatible, FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible. A bilingual cable allows the connection of older devices to the newer port. In 2003, Apple was the first to introduce commercial products with the new connector.

The full IEEE 1394b specification supports data rates up to 3200 Mbit/s (i.e., 400 megabytes/s

Megabyte

) over beta-mode or optical connections up to 100 metres (328.1 ft) in length. Standard Category 5e

Category 5 cable

Category 5 cable is a twisted pair cable for carrying signals. This type of cable is used in structured cabling for computer networks such as Ethernet. It is also used to carry other signals such as telephony and video. The cable is commonly connected using punch down blocks and modular connectors...

unshielded twisted pair supports 100 metres (328.1 ft) at S100. The original 1394 and 1394a standards used data/strobe (D/S) encoding

Data strobe encoding

Data strobe encoding is an encoding scheme for transmitting data in digital circuits.It uses two signal lines , Data and Strobe...

(renamed to alpha mode) with the cables, while 1394b added a data encoding scheme called 8B10B referred to as beta mode.

Beta mode is based on 8B/10B (Gigabit Ethernet & Fibre Channel). 8B/10B encoding involves expanding an 8 bit data word into 10 bits, with the extra bits after the 5th and 8th data bits. The partitioned data is sent through a Running Disparity calculator function. The Running Disparity calculator attempts to keep the number of 1s transmitted equal to 0s, thereby assuring a DC-balanced signal. Then, the different partitions are sent through a 5B/6B encoder for the 5 bit partition and a 3B/4B encoder for the 3 bit partition. This gives the packet the ability to have at least two 1s, ensuring synchronization of the PLL at the receiving end to the correct bit boundaries for reliable transfer. An additional function of the coding scheme is to support the arbitration for bus access and general bus control. This is possible due to the "surplus" symbols afforded by the 8B/10B expansion. (While 8-bit symbols can encode a maximum of 256 values, 10-bit symbols permit the encoding of up to 1024.) Symbols invalid for the current state of the receiving PHY indicate data errors.

FireWire S1600 and S3200

In December 2007, the 1394 Trade Association announced that products would be available before the end of 2008 using the S1600 and S3200 modes that, for the most part, had already been defined in 1394b and was further clarified in IEEE Std. 1394-2008. The 1.6 Gbit/s and 3.2 Gbit/s devices use the same 9-conductor beta connectors as the existing FireWire 800 and will be fully compatible with existing S400 and S800 devices. It will compete with the forthcoming USB 3.0

USB 3.0

.

S1600 (Symwave) and S3200 (Dap Technology) development units have been made, with the latter having falsely promised a consumer version by late 2010.

FireWire S800T (IEEE 1394c-2006)

IEEE 1394c-2006 was published on June 8, 2007.

It provided a major technical improvement, namely new port specification that provides 800 Mbit/s over the same 8P8C (Ethernet) connectors with Category 5e cable, which is specified in IEEE 802.3 clause 40 (gigabit Ethernet over copper twisted pair) along with a corresponding automatic negotiation that allows the same port to connect to either IEEE Std 1394 or IEEE 802.3

IEEE 802.3

IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications...

(Ethernet

Ethernet

Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

) devices.

Though the potential for a combined Ethernet and FireWire 8P8C port is intriguing, , there are no products or chipsets which include this capability.

Future enhancements (including P1394d)

A project named IEEE P1394d was formed by the IEEE on March 9, 2009 to add single mode fiber as an additional transport medium to FireWire.

Other future iterations of FireWire are expected to increase speed to 6.4 Gbit/s and additional connectors such as the small multimedia interface.

Operating system support

Full support for IEEE 1394a and 1394b is available for Microsoft Windows

Microsoft Windows

, FreeBSD

FreeBSD

FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...

, Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

, Apple Mac OS 8.6 through Mac OS 9

Mac OS 9

Mac OS 9 is the final major release of Apple's Mac OS before the launch of Mac OS X. Introduced on October 23, 1999, Apple positioned it as "The Best Internet Operating System Ever," highlighting Sherlock 2's Internet search capabilities, integration with Apple's free online services known as...

, Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

, NetBSD

NetBSD

NetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...

, and Haiku

Haiku (operating system)

Haiku is a free and open source operating system compatible with BeOS. Its development began in 2001, and the operating system became self-hosting in 2008, with the first alpha release in September 2009, the second in May 2010 and the third in June 2011....

.

In Windows XP, a degradation in performance of 1394 devices may have occurred with installation of Service Pack 2. This was resolved in Hotfix 885222 and in SP3. Some FireWire hardware manufacturers also provide custom device drivers which replace the Microsoft OHCI host adapter driver stack, enabling S800-capable devices to run at full 800 Mbit/s transfer rates on older versions of Windows (XP SP2 w/o Hotfix 885222) and Windows Vista. At the time of its release, Microsoft Windows Vista

Windows Vista

Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...

supported only 1394a, with assurances that 1394b support would come in the next service pack. Service Pack 1 for Microsoft Windows Vista

Windows Vista

has since been released, however the addition of 1394b support is not mentioned anywhere in the release documentation. The 1394 bus driver was rewritten for Windows 7 to provide support for higher speeds and alternative media.

In Linux, support was originally provided by libraw1394 making direct communication between user space and IEEE 1394 buses. Subsequently a new kernel driver stack, nicknamed JuJu, has been implemented.

Cable TV system support

Cable TV providers (in the US, with digital systems) must, upon request of a customer, provide a high-definition capable cable box

Set-top box

A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...

with a functional FireWire interface. This applies only to customers leasing high-definition capable cable boxes

Set-top box

from their cable provider after April 1, 2004. The relevant regulation is 47 CFR 76.640 Section 4 Subsections i and ii.
The interface can be used to display or record Cable TV, including HDTV programming.

Comparison with USB

While USB 2.0 (introduced in 2001) is quoted as running at a higher signaling rate (480 Mbit/s) than legacy FireWire 400 (400 Mbit/s, available since 1995), data transfers over S400 FireWire interfaces generally outperform similar transfers over USB 2.0 interfaces in real world environments. Few if any USB 2.0 device implementations are capable of saturating the entire 480 Mbit/s, but this can be achieved with multiple devices on the same bus. In real world tests USB hosts rarely can sustain transfers exceeding 280 Mbit/s, with 240 Mbit/s being normal. This is likely due to USB's reliance on the host processor to manage low-level USB protocol, whereas FireWire delegates the same tasks to the interface hardware (requiring less or no CPU usage). For example, the FireWire host interface supports DMA and memory-mapped devices, allowing high-level protocols to run without loading the host CPU with interrupts and buffer-copy operations. It should also be noted that FireWire features two data buses for each segment of the bus network whereas USB only features one. This means that FireWire can have communication in both directions at the same time, but with USB communication can only occur in one direction at any one time.

Other differences are that FireWire uses simpler bus networking, provides more power over the chain and more reliable data transfer, and is less taxing on a CPU. USB requires the presence of a bus master, typically a PC, whereas FireWire is a true peer-to-peer network, thus allowing either device to serve as the host or the slave.

Automobiles

IDB-1394 Customer Convenience Port (CCP) is the automotive version of the 1394 standard.

Wind power turbines

Audio monitoring for vibrations in the power transmission in wind driven electrical turbines uses a 1394 network for data gathering.

Networking over FireWire

FireWire can be used for ad-hoc (terminals only, no routers except where a FireWire hub is used) computer network

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

s. Specifically, RFC 2734 specifies how to run IPv4

IPv4

Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...

over the FireWire interface, and RFC 3146 specifies how to run IPv6

IPv6

Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

.

Mac OS X, Linux

Linux

, and FreeBSD

FreeBSD

include support for networking over FireWire. Windows Me

Windows Me

Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....

, Windows XP

Windows XP

Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

and Windows Server 2003

Windows Server 2003

Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...

include native support for IEEE 1394 networking. Windows 2000

Windows 2000

Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...

does not have native support but may work with third party drivers. A network can be set up between two computers using a single standard FireWire cable, or by multiple computers through use of a hub. This is similar to Ethernet

Ethernet

networks with the major differences being transfer speed, conductor length, and the fact that standard FireWire cables can be used for point-to-point communication.

On December 4, 2004, Microsoft announced that it would discontinue support for IP

Internet protocol suite

The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...

networking over the FireWire interface in all future versions of Microsoft Windows

Microsoft Windows

. Consequently, support for this feature is absent from Windows Vista

Windows Vista

and later Windows releases.
Microsoft rewrote their 1394 driver in Windows 7 but networking support for FireWire is not present. Unibrain offers free FireWire networking drivers for Windows called ubCore which support Windows Vista and later versions.

The PlayStation 2

PlayStation 2

The PlayStation 2 is a sixth-generation video game console manufactured by Sony as part of the PlayStation series. Its development was announced in March 1999 and it was first released on March 4, 2000, in Japan...

console had an i.LINK-branded 1394 connector. This was used for networking until the release of an Ethernet adapter late in the console's lifespan, but very few software titles supported the feature.

IIDC

IIDC (Instrumentation & Industrial Digital Camera) is the FireWire data format standard for live video, and is used by Apple's iSight

ISight

iSight is a webcam, both external and internal, developed and marketed by Apple Inc. The external iSight was sold retail for US$149, connected to a computer via a FireWire cable, and came with a set of mounts to place it atop any then-current Apple display, laptop computer, all-in-one desktop...

A/V camera. The system was designed for machine vision

Machine vision

systems but is also used for other computer vision

Computer vision

Computer vision is a field that includes methods for acquiring, processing, analysing, and understanding images and, in general, high-dimensional data from the real world in order to produce numerical or symbolic information, e.g., in the forms of decisions...

applications and for some webcams. Although they are easily confused since they both run over FireWire, IIDC is different from, and incompatible with, the ubiquitous AV/C (Audio Video Control) used to control camcorders and other consumer video devices.

DV

Digital Video (DV

DV is a format for the digital recording and playing back of digital video. The DV codec was launched in 1995 with joint efforts of leading producers of video camcorders....

) is a standard protocol used by some digital camcorder

Camcorder

A camcorder is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage...

s. All DV cameras that recorded to tape media had a FireWire interface (usually a 4-conductor). All DV ports on camcorders only operate at the slower 100 Mbit/s speed of FireWire. This usually gives problems where the camcorder is daisy chained off a faster device (such as a disc drive).

Labeling of the port varies by manufacturer, with Sony using either its i.LINK trademark or the letters 'DV'. Many digital video recorder

Digital video recorder

A digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...

s have a "DV-input" FireWire connector (usually an alpha connector) which can be used to record video from a directly-connected DV camcorder ("computer-free").

The protocol also allows remote control (play, rewind, etc.) of connected devices and also streaming of the time code from a camera.

It was not possible to use a USB interface for tape based systems because the video was streamed from the tape at a constant rate. USB relied on processor support and this was not guaranteed to service the USB port in time. The recent move away from tape towards solid state memory or disc media (e.g. SD Cards, DVD or Hard Drives), has enabled a switch to USB.

Frame grabbers

IEEE 1394 interface is commonly found in frame grabbers, devices that capture and digitize an analog video signal; however, IEEE 1394 is facing competition from the Gigabit Ethernet

Gigabit Ethernet

Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...

interface (citing speed and availability issues).

Security issues

Devices on a FireWire bus can communicate by direct memory access

Direct memory access

Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....

(DMA), where a device can use hardware to map internal memory to FireWire's "Physical Memory Space". The SBP-2 (Serial Bus Protocol 2

Serial Bus Protocol 2

Serial Bus Protocol 2 standard is a transport protocol within Serial Bus, IEEE Std 1394-1995 , developed by T10....

) used by FireWire disk drives uses this capability to minimize interrupts and buffer copies. In SBP-2, the initiator (controlling device) sends a request by remotely writing a command into a specified area of the target's FireWire address space. This command usually includes buffer addresses in the initiator's FireWire "Physical Address Space", which the target is supposed to use for moving I/O data to and from the initiator.

On many implementations, particularly those like PCs and Macs using the popular OHCI

OHCI

A host controller interface is a register-level interface that enables a host controller for USB or FireWire hardware to communicate with a host controller driver in software...

, the mapping between the FireWire "Physical Memory Space" and device physical memory is done in hardware, without operating system intervention. While this enables high-speed and low-latency communication between data sources and sinks without unnecessary copying (such as between a video camera and a software video recording application, or between a disk drive and the application buffers), this can also be a security or media rights-restriction risk if untrustworthy devices are attached to the bus. For this reason, high-security installations will typically either purchase newer machines which map a virtual memory

Virtual memory

In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...

space to the FireWire "Physical Memory Space" (such as a Power Mac G5, or any Sun workstation), disable relevant drivers at operating system level, disable the OHCI

OHCI

A host controller interface is a register-level interface that enables a host controller for USB or FireWire hardware to communicate with a host controller driver in software...

hardware mapping between FireWire and device memory, physically disable the entire FireWire interface, or opt not use FireWire hardware.

This feature can be used to debug a machine whose operating system has crashed, and in some systems for remote-console operations. On FreeBSD, the dcons driver provides both, using gdb as debugger. Under Linux, firescope and fireproxy exists.

External links

1394 Trade Association
http://www.1394ta.org/developers/specifications/StandardsOrientationV5.0.pdf 1394 Standards Orientation, Introduction.]
High-Definition Audio-Video Network Alliance (HANA) Standard using IEEE 1394 FireWire for interconnecting A/V components
Apple FireWire Technology
IEEE 1394 Firewire connectors pinout

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.